Perhaps with your grand kids but not with moving targets in general. There are highly controlled tests of that kind carried out by the French laboratory called FNAC for example.

For clarity sake. I specifically cited my issues in regards to shooting photographs of my grand kids in their usual habitat and activity level. That is a primary reason I bought the 20 mm as soon as it was announced. It is also relevant that it was, outside of legacy lenses, the only choice for a quality fast prime at the time (as a side note I think the introduction of the 20 mm was a critical positive turning point for mFT in the market). Frankly, at the time and continuing, studies that control for "moving targets in general" are not relevant for my primary purpose of use.

I do not discount the other tests and reviews. Actually, the contrary is true. These objective tests confirm my 'field observations' that the 20 can be problematic under certain conditions - the very conditions of most importance to my use of the lens.

Now if you know of a controlled study of AF performance in a Chuck e Cheese, with a dozen active 3 year olds in constant movement all across a large room please provide me with the citation. I'm interested in knowing if it confirms or not my field observations (as anecdotal as they are) or the observations of the other grand parents or parents who have posted identical experiences.

Sorry to make you disappointed. No I don't know of "a controlled study of AF performance in a Chuck e Cheese, with a dozen 3 year olds in constant movement all across a large room". I also think you know fully well that such a study is not possible. So why did you ask?

Yes I do. To make a point that you made so well: "The main reason, however, that tests are insufficient is that there are too many potentially different situations for tests to cover them all well enough."

Well, if that is your point, it's off target. Hence my question.

To ask for a controlled test in an environment that is obviously uncontrollable is to ask for the impossible. The contention of mine to which you refer is that testing can never be perfectly exhaustive, which is something entirely different.

My point is I often find myself in one of these "different situations". An outlier from what you often describe as "normal", ordinary, etc. So tests that do not address this outlier state or not relevant.

Whether you often find yourself in a different situation than those to which available tests apply is yet to be determined. Hence the request of mine below to which you didn't respond.

I've had the 20 since launch. I think very highly of its objective measurements and how they manifest themselves in the photographs under approximately 90% of the my shooting situations.

But. The problem with slow focus, especially hunting, is problematic in situations where I need exceptionally fast focus, i.e., when indoors and I can't demand that everything be perfectly controlled on behalf of the lens.

In many earlier threads on the subject, I have pointed out that there are indeed conditions where the AF of the 20 will be slower than that of other lenses. One of them is when it hunts (although it is not more prone to hunting than other lenses, just slower when it does it). Another is when you focus between extremes, like from minimum focus distance (0.2 m) to infinity (but 0.75 to infinity as in my test is not a problem). A third situation for which the lens is not suited is AF-C (on Pany bodies it won't even be allowed to enter that mode) and a fourth is video (if you want to AF during a clip).

However, I am hard pressed to think of a situation where it is practically important to quickly AF from 0.2 m to infinity and as to hunting, the practical solution is simply not to allow the lens to hunt or hunt to completition. This is largely a matter of knowing your equipment, its limitations, and how to overcome them.

Do you realize how condescending this sounds? I know my "equipment, its limitations, and how to overcome them". In fact, that's why I also know that there are subjects and conditions of great importance to me where your constantly repeated work-arounds (always implying that the photographer is at fault) can not overcome the 20's limitations. In regards to my 20, I know my "equipment, its limitations" well enough to know that to overcome them I needed to invest in a lens without these specific limitations. In my case the 12-40 (along with other reasons to 'need' this lens). Based on other posts, some have concluded to overcome the 20's limitations in similar conditions by replacing it with the 17 1.8.

Since you know your equipment, its limitations, and how to overcome them so well, I am sure you can easily specify a target and a light situation where an f/1.7 lens fails to lock (which I assume is the limitation you have in mind; if not please correct me). So please provide a visual illustration of such a target, the light situation you want me to consider (ISO, f-stop, shutter speed) and its relevance for "action" photography of the kind where you experience problems.

First, we are not talking about "an" 1.7 lens, we're talking about the Pany 20mm 1.7 and in my case mounted on a E-M5.

You didn't respond to my request. Please do.

As to "an" 1.7 lens versus the Pany 1.7, are you saying that there is a material difference with regard to the propensity to hunt (which, since you didn't correct me and I asked to be corrected if wrong, is the property I assume you have in mind)? If so, why would that be?

BTW: The body on which I currently use the 20/1.7 (and with which I conducted most of my testing) is the E-M5. So we can eliminate at least that variable.

Second, when I shooting indoor, low light, high activity kids parties I'm not testing to determine causation so I don't keep the data in an attempt to find the cause and work-around.

Me neither.

Again as you said this would be an insufficient test anyway because the next shot be a different situation (different set of variables in play), but within the limitations range of the 20.

It seems you misunderstood me. See my very first point above.

Repeated disappointing results however was sufficient for me to switch lenses for this outlier and keep the 20, and be quite happy, in the "normal" and "ordinary" where I think it shines. Others have chosen the 17.

No problem with any of that.

I will keep the 20. There are times when the combination of its objective measurements are superb and make it to the photograph. I was going to buy the 17 for the situations where the combination of the 20's objective measurements are less far less than superb - sharpness doesn't count if I miss the fleeting moment of a child's experience. I abandoned this idea when the 12-40 was announced and purchased it instead. Even though some of its objective measures (and some subjective such as size & bulk) are less than superb or ideal, it is now constantly on my camera because it gives me a higher keeper rate in less than "strictly controlled conditions".

BTW, I admire your analytical thinking, but hope you also understand that it is often extremely difficult to parse and control individual variables, permutations and their interfaces in the messy real world of application, especially when you throw people into the System such as photographer+camera+lens+lighting+subject .... Analytical thinking is entirely correct for mechanical testing and reviews. However, its necessary, but not sufficient. Move to the application of people taking photographs and Systems thinking, for me, is certainly messy, but very informative in the sense that posts from users here give me an understanding of the Systems behavior in situations important to me. That is, I rely on both objective analysis of tests and subjective posts of users to whom I relate because my performance criteria aligns with theirs. We often shoot similar subjects under similar conditions.

I understand all of the above. The main reason, however, that tests are insufficient is that there are too many potentially different situations for tests to cover them all well enough. Consequently, I too listen to the experiences of others. Sometimes, however, I find reason to question that reports about such experiences are valid descriptions of the objective facts. As I hope you realize, the step from subjective experiences to objective facts is sometimes a very long and complicated one.

Of course I do. That's why I brought it up. And, why I totally discount some experiences that are too distant from the objective facts (e.g., recent posts that the '75 is disappointing' or the constant 'you can't get sharp photos with the 75-300).

So how do you decide how far from the objective facts "user experiences" are without first having tested in order to determine what the objective facts are actually like?

As I said from tests and reviews: "I do not discount the other tests and reviews." And use them to evaluate observations from the field: "These objective tests confirm my 'field observations' that the 20 can be problematic under certain conditions - the very conditions of most importance to my use of the lens." What I didn't specifically say, but I'm happy to is that this includes comparing other's field observations with these same tests and reviews.

What objective tests of the AF behavior of the 20 are you thinking of? Please be as specific and exhaustive as you can.

The 20/1.7 and its AF behavior is a case in point here. I have seen quite a few forum members recognize, after discussing the matter in detail, that perceptual complications play a part in the impression that the AF of the 20 is slow. One of these is that you hear the lens AF (in sufficiently quite surroundings), which is likely to strengthen the impression of duration. Another is that the slow hunting behavior is what is most likely to make a lasting impression.

Again condescending. Do you think you are the only one intelligent enough to understand power of perceptions? I based my decision to limit my use of the 20 and move to the 12-40 based on the real, and very simple, observation that it is in actuality slow to lock, not lock or hunt at the few, but critically important, times I need it to be 'blazingly' (and I know obtuse words like this drive you crazy) fast.

No, the word "blazingly" doesn't drive me crazy. But since you think it does, why did you use it?

To make a point.

What point?

If another poster uses a subjective adjective you are quick to ask for a definition.

Only when it matters.

I assumed that this was because of your penchant for precise objectivity. Sorry I was wrong.

You weren't in that regard.

It appears that precision and objective descriptions are acceptable to you.